Subject: Re: ESMTP Services Advertisement Requirements? RFC 821 Esoteric Commands Exclusion Permitted?

From: Jaap Akkerhuis <[email-masked]>
Date: Mon, 19 Jan 2004 23:11:41 +0100

What are your thoughts?  
    
RFC 2821 obsoletes 821, 974, 1869 and updates 1123. Maybe you find some
answers there?

	jaap

---

From: "Sabahattin Gucukoglu" <[email-masked]>
Date: Mon, 19 Jan 2004 21:39:31 -0000

Hi people,

For STD 10, RFC 1869, SMTP Service Extensions, it is not made clear, 
except possibly in a pair of examples provided by that memo, exactly 
whether or not the commands defined as optional and not required for a 
minimum implementation of SMTP (RFC 821), should or should not be 
advertised as described by the Service Extensions listings maintained by 
IANA in the manner described by RFC 1869.  In fact, no mandates are set 
upon the specific advertisement of any service, be it supported or not, of 
RFC 821 origin or otherwise.  Specifically, since the standard 
implementation of SMTP in RFC 821 makes no requirement for advertising 
optional commands that may be implemented (HELP, EXPN, SAML, SOML, etc), 
is it a violation of RFC 1869 that the server, despite supporting those 
features of RFC 821, does not advertise any or some of those supported 
commands in the ESMTP ehlo response, even if they are available for 
service in normal use of SMTP?  Since they were defined as extensions only 
when the extensions framework was built, it seems unreasonable to expect 
implementations which may support the ESMTP framework to necessarily 
advertise those commands, rather than the few new ESMTP extensions such as 
Auth and StartTLS that the framework support was probably designed to 
cater for and for which developers have incorporated support into their 
mail transports.  Not advertising features of SMTP will slightly decrease 
the transaction overhead without impact, in all probability, since the 
assumption can safely be made that those esoteric features of SMTP that 
are of any use to a specific client are called usually with prior 
knowledge of the features provided by the server, as in the use of turn or 
help in normal RFC 821 usage.  Finally, many SMTP services out there 
exhibit this exact behaviour, not advertising supported features of SMTP 
in their ESMTP synopsis, so it is of interest to me to know whether, as 
part of the configurability of a mail transport, the option to advertise 
any, all, or all except RFC821 specific optional commands should be made 
available, or even whether or not the advertising of any service, of 
whatever origin, is required at all in any case.  The help verb may then 
list all verbs which are supported, inclusive of those defined by RFC 821 
or otherwise excluded for administrative reasons.  

What are your thoughts?  

Cheers,
Sabahattin
-- 
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    A penny saved is ridiculous.

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